| 摘要 |
PURPOSE:To suppress a transient current and start an electric power supply rapidly, by a method wherein in starting an electric power supply, the output voltage of a converter is made to correspond to the residual voltage of an induction motor before it is driven. CONSTITUTION:While an induction motor 15 is being fed from AC buses R2, S2 and T2 through switches 16, if the switches 16 are opened, a residual voltage having a voltage value VM and a frequency fM is generated in the induction motor 15. The voltage value VM detected in a residual-voltage detector 19 is inputted to a voltage controller 2 in a voltage controlling circuit 9 through a switch 4b which is closed only when an electric power supply is started. In addition, the difference between the phase of the residual voltage VM controlled in an automatic phase controller 21 and that of the output voltage of an inverter 10 is inputted to a mixing circuit 13 in a frequency controlling circuit 14 through a switch 4c which is closed only when an electric power supply is started. Thereby, the phase of the output voltage of the inverter 10 follows that of the residual voltage of the motor 15. Accordingly, if immediately after the switches 16 have been opened, switches 22 are closed to start an electric power supply from a converter 30, no transient current flows. |
